Aspen Plus simulation for effluent reuse in thermomechanical pulp mills

Area of Science:

• Chemical Engineering
• Environmental Science
• Pulp and Paper Technology

Background:

• Pulp and paper mills consume significant amounts of fresh water.
• Wastewater treatment and effluent reuse are crucial for sustainable industrial operations.
• Closing water circuits in pulp production can reduce environmental impact and operational costs.

Purpose of the Study:

• To evaluate the feasibility of closing the water circuit in thermomechanical pulping (TMP) production.
• To assess the impact of reusing treated effluent on TMP quality and process elements.
• To determine optimal proportions for treated effluent replacement of well water in TMP manufacturing.

Main Methods:

• Simulations using Aspen Plus® to model TMP production with treated effluent reuse.
• Dynamic simulation to analyze non-process element (NPE) accumulation at various reuse percentages (50%, 75%, 100%).
• Laboratory bleaching tests to evaluate final pulp brightness and brightness reversion.

Main Results:

• Simulations indicated manageable concentrations of manganese, iron, and copper with up to 100% effluent reuse.
• Pulp brightness and brightness reversion remained comparable to fresh water use across all tested effluent reuse scenarios.
• No significant negative impact on final pulp quality was observed with treated effluent integration.

Conclusions:

• Treated effluent can be effectively reused in TMP production without compromising product quality.
• Closing the water circuit through effluent reuse offers a viable strategy for reducing water consumption in pulp mills.
• The study supports the environmental and economic benefits of implementing water recycling in the pulp and paper industry.